1. Field of the Invention
This invention relates to positioning and constraining a substrate relative to a read head, more particularly, to an apparatus for positioning magnetically coded substrates relative to a magnetic read head.
2. Description of Related Art
Magnetic encoding and reading provide an electronic manner in which data is obtained. Magnetically encoded characters are printed on a flexible substrate such as paper or plastic. The magnetically encoded substrate is designed to pass across a read head. The magnetic characters are shaped and positioned on the substrate to create variations of magnetic flux that the read head senses, and the magnetic flux is transformed into varying electrical current. The electrical current is provided to electronic conditioning circuitry that permits the characters to be read.
The magnetically encoded substrate should optimally make correct and continuous contact with the magnetic read head. The active reading area of the magnetic read head is a vertical air-gap between two sets of laminated cores. The air gap is approximately four thousandths of an inch or 0.1 millimeters in width. This air gap is the primary location in which magnetic flux variations are generated. The air gap, however, has an edge in which boundary effects occur. Consequently, the substrate should remain in intimate contact with the read head for a distance before and after the air gap.
The contact between the substrate and read head is made as the flexible substrate is contoured around the read head, known in the art as xe2x80x9cwrapping.xe2x80x9d The amount of xe2x80x9cwrap,xe2x80x9d or the portion of the substrate that contours around the read head, is described as a number of degrees. If the xe2x80x9cwrapxe2x80x9d includes too great of an angle, then the substrate is substantially deformed and an unnecessary rotational couple occurs, causing excessive skew and buckle to the substrate. If the xe2x80x9cwrapxe2x80x9d includes an insufficient angle, then a loss in signal strength and quality occurs.
Various combinations of rollers, xe2x80x9cslipperxe2x80x9d springs, flexible elements and similar devices traditionally have been used to mitigate this contact problem between the substrate and the read head.
A further issue regarding contact between the substrate and read head relates to the material from which a device that causes the substrate to wrap about the read head is made. The device is preferably made of materials that are paramagnetic and exhibit no independent magnetic properties. The material of the device must also be able to withstand the constant friction of the substrate material.
The previous use of a paramagnetic stainless-steel alloy, known under the trademark of DYNAVAR(copyright), was conforming, elastic, and compliant creating an extremely highly-finished, and smooth surface with low friction. The wear characteristics of the paramagnetic stainless-steel alloy, however, required regular replacement of the read head apparatus as the continual substrate friction causes degradation.
The present invention is to provide an apparatus for positioning a magnetically coded substrate relative to a magnetic read head. In accordance with the teachings of the present invention a magnetically coded substrate positioning apparatus is disclosed. A beam arm is attached at one end to a housing. A contact head is located at the second end of the beam arm. The contact head has an outer extremity and an inner extremity. A recessed wedge formed by a lead-in and a lead-out is located at the inner extremity. The recessed wedge contacts a substrate in two locations, one point of contact occurs between the lead-in and the substrate, and the other point of contact occurs between the lead-out and the substrate. At these points of contact, a force is applied to the substrate causing the substrate located between said lead-in and lead-out to continuously contact an apex of the read head for a short distance before and after an active reading area of the read head.